Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$71.48	3.153%	$73.7338	$73.73	$73.75	$73.70
Purchase #2	$138.42	4.130%	$144.1367	$144.14	$144.15	$144.10
Purchase #3	$237.85	7.750%	$256.2834	$256.28	$256.30	$256.30
Purchase #4	$92.35	11.625%	$103.0857	$103.09	$103.10	$103.10
Purchase #5	$244.96	9.859%	$269.1106	$269.11	$269.10	$269.10
Purchase #6	$66.77	8.278%	$72.2972	$72.30	$72.30	$72.30
Purchase #7	$114.36	8.325%	$123.8805	$123.88	$123.90	$123.90
7 purchase totals =	$966.19		$1,042.5279	$1,042.53	$1,042.60	$1,042.50